-edward d



UNITED STATES .To' all iiuhom it may concern:

Be it known that I, EDWARD D. KENDALL, a citizen of the United States, residing at Sewaren. in the countyof Middiesex and State 3 of New Jersey, haveinventcd certain newand useful improvements-fertile Recovery of Gold a'nd Silver from Solutions; and I do hereby declare .the following to be a full and exact description thereof. 4 to:- In this application, wherever I use the term sine, I do not wish to be necessarily understood as meaningzinc from which all impurities have been removed, but I wish to be un- 5 jwhich is realiya zinc alio containing zincin {logs metals, such as antimony, arsenic and I 4 I I I do not conline miself to any articular 2o solvent in making t esolution 0 precious metalsfro'm the'om, Necessarily the preci itatlngagent must be such as to be chemica iy active in the presence of such solvent. It is applicable to all processes where a metallic 1! 5 precipitating agent-is used, but'as in the 'resent state of the art,th'e solvent in genera use is an aqueous solution of a cyanide, I will explain my process as applied to that method.

I The cyanide solution-charged with the pre- 3o cious metals has heretofore been snbJected to various processes for the recoveryof the gold and silver, and the object'of' my invention is to furnish a rapid, exhaustive and com para- 'tively inexpensive process for the separation 5 of the'precious from the baser metals contain'ed in the solution, and primarily involves the adaptation and use of a new ;and imroved precipitating reagent and a new and mproved'm'ethod of treating the'rcsulting .40 precipitates. v

' Heretoi'ore,-in the so-called cganide processes the solution has been ma e to perco- -l ate through a. recipitating agent of commlnuted zinc, w e'reby the gold and silver, as

5 well as the baser metals have been deposited ,together 31 pop t he zinc but in these the after recovery ofthe goldatidsi verjfro the precipitate is tedious and only partially eflective. r

o "'Inm he loved rocess lbrin tlt echa s atolutior: int .conta t with a pulgerized Lili gam ofzinc and mercury, hereinafter more 'iation.

'rateiy precipitated.

derstood as referring also to commercial zinc,

' combination with a-smal percentage of va-' 'electrolyt BEST AVAILABLE COPY PATENT OFFICE.

EDWARD D, KENDALL, or sEWaann, NEW JERSEY.

Processor are mm roa-atcovtm'nc SILVER ans GOLD mom SOLUTiONS.

srscmcamer 101111111: m Letters mm rte-seems, dated April so, 1806. I Application filed licmaber Bold. lsrlsl No. 628,061. (No specimcnai fuliy'described, either by agitation or perco- As a result of the chemical and oicctnolytical reaction which takes place and which, may. be, is somewhat hastened by heatilig the solution, the gold and silver are taken upby the mercury oi the amalgam, an equivalent quantity of the zinc in the amalgam takes the place of those metals in the solution and of the baser metals which are sepa- The valuable precipi: late will then consist of gold and silver in the form ofa mercurial amalgam and the excess of zinc amalgam. This excess must be always present, because it is impossible to predetermine exactly how much of the zinc amalgam the solution requires and, therefore, to provide against all contingencies and to secure the certain amalgamation of all the gold and 7c silvercontained. in'the solution, it is practicaliy necessary to supplv the zinc amalgam in aquantity greater than the preliminary assay of the ore might indicate particularly, so as by the next step in any improved pro; 75 cess the zinc is readily separated fromthe other constituent iartsoftheamalgam. -lhis is accomplished iy removing the valuabld precipitate to another vessel. covering it with granulated carbou,the ordinaryhard carbon, such as is used in electrical batteries answers the purpose very well, and then nearl tilling the vessel with a solution of snip uric acldand water in the proportion of about one part of-acid to ten or twelve of water. This combination constitutes the elements of'an electrical voltaic pain, Carbon in the presence of the amalgam and acid solution is chemically inert but electrically active. The 6 action which follows, causes the sine to be rapidly oxidised, dissolved and taken up by the dilute acid. After the'eabau'stio'n of the sine, the amalgam will then practically consist ct gold,sllver and merctgs only, and the precious metals are recove 5 therefrom by the ordinary well known processes, suehas by distilling olt the mercury. The slncamalgam above referred to shou d, of'coursc, bepommlnutsd-latngranules, turns lags, dlings or shavings, butt'o obtain the best and most economical results it should be pul- VIl'liOds" e H K l! metallic mercury sbonldbe added o v pcwder,-there wonld turned 4 i too , cury to threc'ot zinc and after thorough mixlog, and cooling, grinding the amalgam thus .tormed, butI do not coniine myself to any particular proportion or method of producing the powdered amalgam, the essential requirement being as applied to all processes that it shall be an amalgam of mercury with that metal which may be properly used as a precipitant-tor the particular solvent used in the.

original solution. As above sthted,when the solvent is cyanogen, the precipitating agent is an amalgam of zinc and mercury, preterably in the form of powder or granules.

l avlng thus described my invention, what I clailm, and desire to secure by Letters Pat- Ont, 5-

i. In the recovery of gold and silver from cyanide solutions the process of subjecting said solutlonLto the-action nt .apulvsriaed BES T AVAILABLE COPY amalgam, composed of mercury and zinc as described.

the recover) g ld and silverjfro in solntioniuthe process of ransferring the gold and-saver from said solutions to a mercurial amalgam, by first subjecting them to the action of a pulverized or granulatcdamalgam,

substantially as described.

8; The process of the recovery of gold and a 45' silver from solutions which consists of the following steps, (tirst) the subjecting of the ore containing the precious metals to the'action .composed oi mercury and an appropriate me- T; taliic reagent and then' treating the.valnableprecipitate to the action of granulated carbon f 1 in contact therewith in a bath of dilute acid,

of a solvent, thus obtaining an aqueous soiution 0! the solventand the minerals contained in the ore, ssecond) subjecting the 's'aidseln tion to the e ectro-chemical action otame'reurial amaigam, (third subjecting the valuable precipitate secured y the preceding process to the action of dilute acid in the presence of carbon, (fourth) the recovery ofthe-vaiuable metal from the result of the preceding pro cess. substantially as described.

' anwaao n. KENDALL.

in presence of- Jastas W.-iiuouxs, Sana. V. BILLINGS. 

